The mounting of components to support structures in operating environments of wide variations in temperature requires prudent engineering design when materials of different thermal coefficients of expansion are involved. Differential thermal growths of the component and the support structure can create significant mechanical stresses at their points of attachment and ultimate fatigue failure when the parts undergo frequent thermal cycling. Another important design consideration in many applications is maintaining the mounted component in a fixed position relative to the support structure despite wide variations in temperature.
An application where both fatigue failure and positioning considerations are of critical importance is the mounting of transmission operating components to the transmission case. Transmissions, such as hydromechanical steering transmissions in military vehicles, e.g., tanks, are subjected to temperatures cycling over a wide range. From cold starts in sub-zero temperatures, a tank transmission can heat up to several hundred degrees Fahrenheit in service. The transmission operating components are typically made of steel, while the mounting case is typically aluminum to save weight. The different coefficients of expansion of steel and aluminum result in different thermal growths at the common points of mounting attachment between the component and case. With repeated thermal cycling, the stresses generated at these attachment points can ultimately lead to fatigue failure of one of the parts, most typically the aluminum case. Moreover, this different thermal growth can alter the crucial alignment between transmission operating components, causing undo bearing and gear wear and other adverse consequences.